This invention relates to electronic insect detection systems, and particularly to a system for detecting insects by detecting ultrasonic signals generated by the feeding of insects.
Hidden infestations of insects feeding and growing in wood and wood products, in seeds, and in other plant materials cause enormous economic loss in the United States each year. If, however, these infestations can be detected in their early stages and quantitatively assessed, potential damage can be predicted and timely pest management procedures such as fumigation or insecticide treatment can be implemented to prevent serious losses.
Discovery of infestations in their early stages by visual inspection is time consuming and ineffective because the number of insects involved is small, and the insects are tiny and usually hidden from view. Insect infestation begins with low levels of invasion of the product by the insect. Often an adult insect deposits eggs on the product from which immature stages of the insect (i.e., larvae) emerge and begin feeding and growing. Once the immature insects grow to maturity they begin reproducing, thereby increasing the severity of infestation and increasing the loss.
In studying insect biology and behavior, measuring plant damage by insects, or estimating insect numbers, the most appropriate variable to measure is usually the level of insect feeding activity.
Heretofore, insect detection systems which detect insect activity by detecting sound generated by insects have done so by detecting sound in the audio frequency range (20-20,000 Hz). In the audio frequency range, many sounds are detected which are not necessarily the result of insect feeding. These background noises, which mask the targeted feeding sounds, may be produced by non-feeding insect activity, or other environmental stresses on the plant tissue.
Previous insect detection devices have typically used transducers in the range of 200 Hz to 10,000 Hz. In order to isolate the detection system from background environmental noises, it was often necessary to construct a soundproof box to surround the transducer. The design of the soundproof box was often a difficult and time consuming task.
Applicants have found that technology commonly known as "Acoustic Emission" technology can be advantageously used in detecting insects. Heretofore, Acoustic Emission technology has primarily been used in the field of nondestructive testing of metal parts and assemblies. The component under test is subjected to a static stress which causes cracks in the metal part to grow (increase in length). As the crack grows, internal stresses around the crack tip are released which give rise to mechanical disturbances within the material. A transducer capable of converting mechanical waves to electrical signals is used to record the mechanical disturbances (acoustic emissions), thus providing some information related to the rate of crack growth.
Applicants have found that feeding insects produce ultrasonic signals which can be detected by the use of Acoustic Emission technology. As an insect feeds, it tears the fibrous tissue it is feeding on. The tearing of the fibrous tissue creates mechanical disturbances which propagate throughout the material on which the insect is feeding. These mechanical disturbances generate ultrasonic signals which can be detected by the use of Acoustic Emission technology.
An object of this invention is to provide an insect detection system which detects acoustic emissions emanated by feeding insects and which is relatively immune to background noise.
Another object of this invention is to provide an insect detection system which detects insects by detecting ultrasonic signals caused by insects feeding on material.
In accordance with the present invention, an apparatus for detecting insects includes means for detecting ultrasonic signals generated by the feeding of insects and generating first electrical signals therefrom. The invention further includes means for processing the first electrical signals to generate therefrom information about the feeding activity of the insects.
The insect detector of this invention uses an ultrasonic detecting device which is preferrably sensitive to frequencies in the 40,000 Hz range. The use of the ultrasonic detecting device minimizes the effect of environmental background noises bcause the environment is relatively quiet in the frequency range above human hearing (20-20,000 Hz). Most human activities do not generate much acoustic energy at ultrasonic frequencies. Therefore, the sounds detected by the transducer are essentially those resulting from ultrasonic mechanical disturbances propagating through a material caused by the tearing of plant tissue during insect feeding activity. The ultrasonic mechanical disturbances are directly related to the action of the insect's mouthparts tearing the material during feeding. Each mechanical disturbance produced by an insect tearing the fibrous tissue, in other words taking a "bite" out of the material, will be termed a "feeding event."
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.